Just from looking at the picture, my concern about lancing that swelling is, what if it is actually a hernia, and the color of it is due to milk trapped in herniated intestine. You definitely do not want to puncture intestine. Punctured or not, a herniated intestine can be a very serious condition, or can quickly become one if it is not already.

Infection usually first signals itself as pinker or redder skin than usual, and general swelling. Did you notice any in the last few days? A pus pocket would develop later in the infection process. Even then, a pus pocket does not necessarily indicate that the infection is resolving -- only that the by-products of infection have found a space to accumulate in.

To be on the safe side, I would take this little one to a veterinarian without delay. Whether it is an infection or a hernia, it is better to have professional eyes and hands on the case. That's my opinion, based on the picture you posted.

Keep us updated. We care.

_________________ Zephyr Coco Bobby Noche Paiva April I loved you so / I still do / I always will / 'Twas Heaven here with you.

Update It ended up being an infection. I was able to determine this and went along with the laceration process. Afterward, she was treated with microbial hydrogel and returned to the mother. Today I looked at her belly and the previous hole has closed and there is no more redness. Her belly button is looking perfect for a late-developing pup. The area looks 100% the same as the others in her litter did before it disappeared altogether. Thank you so much for all your concern and I'll keep everyone informed. I will post a picture once my husband comes home to help me take it. At this age, all the babies are super squirmy!